Usually when railway cars are taken out of a train and parked at a siding or yard, the hand brakes on at least some of the cars are applied as a precaution against unwanted or unexpected movement of the cars. A typical hand brake may consist of an apparatus for manually applying a brake shoe or shoes to one or more wheels of a railway car by turning a handwheel or pumping a handle connected by gears and/or linkages to the brake shoe engaging mechanism and a mechanism for releasing the hand brake and causing the brake shoe or shoes to be disengaged from contact with the wheels.
A typical railway car hand brake can be released by turning the handwheel or pivoting a release lever. Pivoting the release lever will cause full release of the hand brake preferably without spinning the handwheel or moving the handle used to apply the brakes. This type of system is sometime referred to as a "quick release" hand brake. Prior to the present invention, the hand brakes were manually released separately on each car or on each end of a car equipped with hand brakes at each end and it is possible that the hand brakes may not all have been released when a train or group of cars are moved. When this occurs one or more of several serious problems can result. Among them are worn brake shoes, brake heads and wheel treads, cracked or broken wheels from overheating, worn rail heads, impaired truck action and damage to trucks. All of these conditions are detrimental and costly because they waste power and cause damage to trains and lading.
It is desirable to avoid these undesirable conditions and unnecessary expense by providing an apparatus to reduce or eliminate inadvertent unreleased hand brakes or parking brakes. The terms "parking brake" or "hand brakes" as used herein are intended to include not only the conventional hand brakes described above which are usually applied and released manually by a mender of the train crew but also brakes which can be applied or released from a remote or central control point such as the locomotive or caboose and which may utilize vacuum, air pressure, electricity or other source of power to activate or release a brake on a standing railway car in a yard or siding. Such hand brakes or parking brakes may include portions of the service brake system. As used herein, the term "service brakes" or "service air brakes" is intended to refer to air brakes usually on a train and controlled from a central location, usually the locomotive of a train, to retard the movement of a train or group of cars connected to a locomotive.
The objectives of this invention are to provide one or more of the following means of avoiding movement of a train with the hand brakes or parking brakes in an applied condition: signalling such condition, providing remote or central control apparatus for applying or releasing parking brakes on a train, and providing apparatus for automatically releasing parking brakes on a train in response to predetermined conditions with or without intervention of a member of a train crew.
Because of the strict operating and safety rules applicable to train operation in the United States and other countries the above objectives must be accomplished without interfering with proper train equipment and operation as required by practices established by the Association of American Railroads and by cognizant government agencies. These practices usually require performance of an air brake test procedure before a train is moved cut of a yard or terminal.